My Next Stirling Model

[Hawke]

I enjoy others sharing of ideas and works in progress. Keeps the forum fresh and inspiring for me so...

Draft of design drawing Ive started.


[tab=20]I have a little experience under my belt now, gained mostly by mistakes or failed attempts of course, so Im off into a new design utilizing things like Stainless Steel and some desirable features Ive seen on other Stirling models or "real" machined engines. The SS I found to use as the cylinder is an inch wider than my last two so Ive calculated up components of my two working gamma engines.
[tab=20]The thermosyphon cooling will be a closed system and plumbed on opposite sides, not quite as shown in the drawing. A peltier module w/heat sink will mount under the tank. A shroud directing the fan wind across the cooling water tank and down to the be directed thru the peltier area and across the cylinder of the engine. Peltier module will be powered by the generator which will be a small magnet motor driven by the engine and mounted with a swivel bracket and belt where it can be turned on/off easily. An outlet box with a USB and proto board is planned. Hopefully the engine will have enough power to run the generator. I plan improved crank and bearing configurations Ive already begun work on. I have SS screen mesh and SS wool for the displacer.
[tab=20]I now have a Airpot graphite piston I may use or mount it in such a way that either it or a diaphragm can be installed. (I changed my last engine from diaphragm to copper cylinder and piston in this way. Interchangeable. The piston is not as airtight as the diaphragm was but had same stroke, and is not as efficient as the diaphragm was.) I am toying with the idea of a slot cut into the wood frame to reduce dead air. A short polished porting maybe just as good here. A similar example of this slot can be seen on YouTube:
http://www.youtube.com/watch?annotation ... KvAWXcKQX4

[tab=20]Although a rough draft the drawing is pretty close to scale but you have to read between the lines somewhat. Its made for my personal use as a guide really.


[tab=20]I am looking for suggestions. My main concern is the ratio conversion calculations I made. How do you think these Proposed dimensions will perform?
Calculations (diaphragm power piston):
Previous
Displacer Cylinder[tab=30]3” x 4 1/2”
Displacer[tab=80]2 1/2” x 3”
Displacer Stroke[tab=40]1”
Power Piston[tab=60]1 1/2”

Proposed (1/3 larger)
Displacer Cylinder[tab=30]4” x 6”
Displacer[tab=80]3 3/8” x 4”
Displacer Stroke[tab=40]1 1/4” - 1 3/8”
Power Piston[tab=60]2”

[Hawke]

I have almost all the parts on hand or in the mail now so its about time to get my fingers busy. Looking forward to comments and suggestions.

[Hawke]

[tab=20]Im just not comfortable with the size of this displacer cylinder and displacer . It just seems it will be too heavy, especially since Im adding weight by using SS materials in the displacer. I just "feel" like a diaphragm of 2" diameter is not enough. I think increasing the diaphragm to 2 in but still using previous cylinder/displacer sizes would be a better way to go. Just find a better stainless bottle and use my 4 inch one for the water jacket enclosure. Anyone else on board with me here or have experience with model stirlings of 4 inch cylinders?
[tab=20]For my purpose I think rpms of 300 are good enough, as my previous models, but Id like a little more torque or overall power. Increasing the dimensions of the power cylinder might do this. Tweaking friction concerns can be done on current stirling but is not going to improve the power aspect much. My goal is to run a small generator to provide maybe 6v to 12v.

[Hawke]

After making the displacer Ive decided to use a smaller diameter SS cylinder.

[Ian S C]

Hawke, remember the ratio, displacer 1.5 the volume of the power cylinder, and the displacer 3 times the diameter, or as near as possible. Ian S C

[fullofhotair]

Hawke,
On the thermosyphon, the more surface area you have , the more it cools. By just blowing air around a big can this exposes very little surface area compared to volume of can. If you cut the middle out of the big can and replaced it with copper pipes running from the top can to the lower can , you would have a radiator , in between. You could even add flat horizontal strips of aluminum or copper sheets between the copper tubes. Iam really looking forward to your peltier cooler.

[Ian S C]

Quite a good type of cooling tower can be made of two sizes of cans, the small dia can,cut the top and bottom out to make a tube, in the large can cut a hole in the bottom to fit the small can, and solder it in. You may cut a disc with a hole to fit the top. Solder in tubes top and bottom for the water in and outlet, and a hole with some sort of plug as a filler. The cool air rises up the inner tube, and greatly improves the cooling. The large vertical BETA motor in my gallery uses this system. This type of tower could be boosted with a small fan pushing air up the in side tube. Ian S C

[theropod2]

Quite a good type of cooling tower can be made of two sizes of cans, the small dia can,cut the top and bottom out to make a tube, in the large can cut a hole in the bottom to fit the small can, and solder it in. You may cut a disc with a hole to fit the top. Solder in tubes top and bottom for the water in and outlet, and a hole with some sort of plug as a filler. The cool air rises up the inner tube, and greatly improves the cooling. The large vertical BETA motor in my gallery uses this system. This type of tower could be boosted with a small fan pushing air up the in side tube. Ian S C

I wonder if a venturi shape, like used on cooling towers at power plants, might help with the "hole" you have used? One could wrap a coil of copper tube around the core venturi shape. Hot water in at the top, and cool water comes out the bottom. I think the use of a small computer fan with a matching sized venturi mouth tower would work very well.

R

[Ian S C]

The one on the motor that I mentioned is made of a bit of sheet metal, wrapped around to make the outer tank 4" dia, the inside tube is an aerosol paint can with the bottom out, and the valve removed, no fan at the moment, it takes about 1 1/2 hrs until the water gets too hot to touch at the bottom, and the motor will run all day, producing 8 watts plus.
Not related, I did an experiment today with my little beam engine, took the flywheel off, and gave it a flip, and it ran quite well, with reduced torque, and not quite so even running compared to with the FW, I'v found that some of my larger motors run without a FW, but with much reduced power. Ian S C

[Hawke]

Slow progress being made. The Displacer Cylinder is Stainless and all components of the displacer are SS as well. Airpot power piston with essentially no dead air space connected right to the top of the D cylinder. My first crank is promising but epoxy or JB Weld is inferior. I took parts to a shop and welded up a prototype. Its ongoing still but looking good so far.

Made a temp crank and flywheel to see how my strokes work and when I put a torch to the engine, it slung the weights off the flywheel! YeeHaw! The flywheel was made from flimsy plastic however and although balanced pretty good epoxy doesnt flex well. Still, all in all its gonna be the strongest and most durable engine yet for me. It actually runs without a flywheel at all.

[Hawke]

Current Aprox Dimensions:
Displacer Cylinder 4” x 1.75”
Displacer 1.5” x 3”
Displacer Stroke 2 ”
Airpot Power Piston Diameter 0.5”
Power Piston Stroke 1.25

[theropod2]

PICTURES!!!

Keep hammerin' away!

R

[Hawke]

Its been a while, lots happened here last few weeks. I have been diagnosed with diabetes, wife was in hospital, and I had been saving up for a welding machine. Ive gotten a little flux core MIG machine and now messing around with a more solid crankshaft design.